9706066 Cohen This Focused Reqearch Group project involves fundamental studies of elastomer properties. The proposed research consists of a three-pronged approach involving: 1) careful synthesis and characterization; 2) use of deuterium NMR; and 3) Monte Carlo simulations. The group will use end-linking chemisty to vary the architecture of the prepared networks in a systernatic way and to examine the effect of this variation on the mechanical and swelling properties of the networks. Deuterium NMR experiments will be used to probe the molecular architecture of the networks and the segment orientational order parameter of networks under compression. Finally, Monte Carlo simulation methods will be developed to examine the molecular structures that are obtained after curing, the swelling mechanisms of the networks and the effect of the chain stiffness of the precursor molecules. Experimental results, model predictions and simulation results will be compared to validate or improve existing models as well as propose new models if necessary. These studies on poly(diethylsiloxane) (PDES) networks will help elucidate a long standing issue about the nature of segment-segment interactions in strained networks because PDES exhibits a mesophasic structure above its glass transition. %%% This research is in the technologically important area of elastomeric materials and networks and will help provide fundamental understanding of their molecular-level structures and properties. ***
